根据两个测距仪传感器采集到的时间和车速数据，推测道路上的汽车型号。
Purpose
The purpose of this assignment is to refresh your programming skills and get
you programming as quickly as possible.
As discussed in class and the first tutorial, for each problem you will be
provided with a description of the problem and a JUnit test class to test your
code. A similar JUnit test class will be used to evaluate your code. You can
use Eclipse or other IDEs to run the JUnit test class to test your code.
Your code must compile. If it does not compile, you will receive a 0 on the
assignment.
Problem: Analyzing Data from a Road Traffic Meter
To analyze how much traffic is on the street, city planners use a Road Traffic
Meter, as shown in the figure below:
The traffic meter consists of two air hoses lying across the lane of traffic.
Every time the wheels of a vehicle roll over both hoses in quick succession,
the meter logs the event as one axle of a vehicle. Two pieces of information
are logged for each event: the time (in milliseconds) and the speed the axle
was traveling at (in kilometers per hour). The traffic meter produces a log of
axle events that look like this:
97205795 51
97205995 52
97207123 45
97207347 44
…
where each line corresponds to a single axle event and is denoted by the time
of crossing and speed.
However, traffic planners need to know how many cars and heavy trucks are
using the street. Your task is to write a program that processes the log and
converts the log of axles to a log of cars and trucks that have crossed the
traffic meter.
Write a program called VehicleCounter.java that reads in a log of axles (as
exemplified above) and outputs the corresponding list of cars and heavy
trucks. Your VehicleCounter class must implement the provided TrafficReporter
interface. This is because your program will be tested via this interface. The
interface contains a single method:
public ArrayList computeTraffic(Scanner input);
—|—
This method must perform the required computation.
Input
The method takes a Scanner object, which contains 0 or more lines of text from
the log produced by a traffic meter. Each line denotes a single event of an
axle crossing the traffic meter. Each line consists of
- an integer of type long, denoting the time in milliseconds; and
- an integer of type int, denoting the speed of the axle in kilometers per hour.
You may assume that there are no errors in the input.
Hint: Use the Scanner object to easily parse the input by using the methods
such as hasNextLong(), nextLong(), and nextInt(), on the Scanner object.
Semantics
The input log will contain a sequence of axles, corresponding to zero or more
vehicles driving down the street. Your vehicle counter must distinguish
between two classes of traffic:
Cars and light trucks are vehicles that have exactly two axles, which are at
least 186cm apart.
Heavy trucks are vehicles that have at least three axles, with one or more
close consecutive axles at the front and one or more close consecutive axles
on the back. Two axles are close if they are less than 186cm apart.
The distance between axles can be computed using the general formula
distance = speed * time
where speed is the average of the two axle speeds and time is the positive
difference between the arrival times of the two axles. Note: The speed of the
axles is given in km/h, the time of arrival is given in milliseconds, and the
minimum distance is in centimeters. You will need to convert the values to
common units in order to get correct results.
Output
The method should return an ArrayList of Strings denoting the class of vehicle
for each set of axles in the input log. If the axles correspond to the car or
light truck, the corresponding String is
T: Car or light truck
and, if the axles in the input log correspond to a heavy truck, the
corresponding String is
T: Heavy truck, F R
where
T is the time, rounded down to the nearest second, of the vehicle’s first axle
crossing the traffic meter.
F is the number of axles at the front of a heavy truck.
R is the number of axles at the rear of a heavy truck.
Examples
Below are a sequence of examples and the corresponding output.
Sample Input
502788 32
503612 33
503775 34
560933 37
561479 36
595629 41
596044 42
650172 56
650780 55
650878 54
650978 53
Sample Output
502: Heavy truck, 1 2
560: Car or light truck
595: Car or light truck
650: Heavy truck, 1 3
Hints and Suggestions
- Your code must compile. If it does not compile, you will receive a 0 on the assignment.
- Your code must be well commented and indented. Please see the Assignments section for this course on Brightspace for Code Style Guidelines.
- You may assume that all input will be correct. You do not need to handle incorrect input, for now.
- The problem in this assignment has a short solution (50 lines of code).
- Be sure to test your programs using the provided JUnit test class.
Grading
The assignment will be graded based on three criteria:
Functionality
“Does it work according to specifications?”. This is determined in an auto-
mated fashion by running your program on a number of inputs and ensuring that
the outputs match the expected outputs. The score is determined based on the
number of tests that your program passes. So, if your program passes t tests,
you will receive T that proportion of the marks.
Quality of Solution
“Is it a good solution?” This considers whether the solution is correct,
efficient, covers boundary conditions, does not have any obvious bugs, etc.
This is determined by visual inspection of the code. Initially full marks are
given to each solution and marks are deducted based on faults found in the
solution.
Code Clarity
“Is it well written?” This considers whether the solution is properly
formatted, well documented, and follows coding style guidelines.
If your program does not compile, it is considered non-functional and of
extremely poor quality, meaning you will receive 0 for the solution.
What to Hand In
Submit the source files for your program in a zip file (.zip). You should have
at least one source file: VehicleCounter.java. If you are using Eclipse, we
recommend that you submit the entire project bundle. Submission is to be done
via Brightspace. Your code must compile. If it does not compile, you will
receive a 0 on the assignment.
